1. Field of the Invention
The present invention relates to the field of downhole fluid analysis. More particularly, the present invention relates to a method of sealing piezoelectric resonators.
2. Description of the Related Art
There is considerable interest in obtaining density and viscosity for fluids downhole at conditions of high temperature and pressure. One technique to obtain density and viscosity measurements of fluids downhole is to dispose a piezoelectric resonator such as a tuning fork in a borehole where the fluids are sampled. The tuning fork is immersed in a downhole fluid having properties that affect the resonance of the tuning fork.
One type of tuning fork is made from a piezoelectric crystal in contact with two electrodes. By sweeping the frequency of an electric signal applied to the electrodes, a real impedance peak and an imaginary impedance peak of the immersed tuning fork can be measured. The peaks can then be correlated to characteristics of the fluid such as density and viscosity.
Unfortunately, manufacturing defects can alter the response characteristics of piezoelectric resonators making them unusable or decreasing their accuracy.